Process of refining copper



, Patented Feb. 20, 1934 PATENT OFFICE PROCESS OF REFINING COPPER JamesWalter Scott, Chicago, Ill., assignor to Western Electric Company,Incorporated, New York, N. Y., a corporation of New York No Drawing,Application October 10, 1931 Serial No. 568,207

9 Claims.

This invention relates to a process of refining copper, and moreparticularly to a method of partially or completely densifying and/ordeoxidizing copper.

v The beneficial effect upon the working properties of copper, such asthose properties necessary in wire-drawing, obtained by using copperdenser than tough-pitch copper which usually contains oxygen to theextent of approximately 10 .03% to approximately .06% by weight togetherwith varying proportions of gases, has not heretofore been fullyappreciated. Also it has heretofore been believed that tough-pitchcopper having the above stated oxygen content was particularly suitablefor the conduction of electricity and that copper having about .05%oxygen therein had the maximum conductivity, the conductivity decreasingrapidly as the percentage of oxygen in the copper WaS increased above.05%

and decreasing somewhat gradually as the percentage of oxygen decreasedfrom .05%. However, it has been determined by extensive experimentationthat with copper of higher purity this theory is probably erroneous, andthat copper increases in electrical conductivity as the vpercentage ofoxygen in the copperdecrease's 1 below .05% if the purity of the copperis correspondingly high. In copper containing relatively large amountsof impurities such as arsenic, antimony, iron, nickel, silicon, etc.,the oxygen counteracts the effect of the impurities on the conductivityand therefore if the oxygen content is reduced below a value determinedby the amount of the impurities the conductivity of the 5 copper willdecrease. The electrical conductivity of copper of high purity as far ashas been accurately determined, consistently increases as the percentageof oxygen is reduced below .05%, so that copper having an oxygen contentof .01% by 40 weight has a conductivity of about 1% higher than copperof the same purity having .05% by weight of oxygen content. Thepercentages of conductivity as mentioned hereinbefore are measured. bythe International Electro-Technical Commission's standard commonly knownas the International Standard.

It is an object of the present invention to provide a method ofproducing high density copper and/or producing copper which has beendeoxidized in any desired amount.

In accordance with one embodiment. the invention which is a continuationin part of my copending application Serial No. 492,877, filed November1, 1930, contemplates a method of producing markedly dense and/ordeoxidized copper by subjecting molten copper in which there is presenta reducing agent such as hydrogen or carbon monoxide gas or solid carbonto a vacu um to remove the absorbed, adsorbed, and dissolved gases,and/or combined oxygen therefrom.

A better understanding of the invention may be had by referring to thefollowing detailed description of one embodiment thereof. It is proposedto melt tough pitch copper in an electric furnace, .preferably of theinduction type, wherein the metal is in motion during the meltingprocess and while the copper is maintained in'a molten state to apply avacuum thereto.

Tough pitch copper produced by the usual commercial method of poling themolten oxidized copper with green poles contains a certain amount ofhydrogen (H2) and carbon monoxide (CO) gases and other reducing gaseswhich are taken up dur ing the poling process. The application of avacuum of 1 to 4 millimeters promotes reactions between the absorbed,adsorbed, dissolved and/orv combined oxygen.in the copper with thehydrogen and carbon monoxide and produces steam (H20) and carbon dioxide(CO2) which'are then withdrawn from the liquid copper by the vacuum,resulting in a materially increased density in the copper due to theelimination of the absorbed, adsorbed, dissolved, and/or combined gaseswhich are drawn off through the vacuum system and expelled into the air.After the vacuum has been applied for a predetermined time the coppermay be cast in the usual manner. It has been determined, for example,that 300 grams oftough pitch copper maintained at a temperature of 1150C. and subjected toa vacuum of 2 millimeters of mercury will becompletely deoxidized and practically freed from gases in approximatelythree minutes.

Copper refined in accordance with the above outlined method has beenfound to contain so ,v little oxygen that the copper will not becomeembrittled if heated in a hydrogen atmosphere of 900C. for 30 minutes. v

For most commercial purposes, however, completely deoxidized copper isnot required, hence it may be sufiicient in the production. ofcommercialgrades of copper to employ a lower temperature, a lower degree ofvacuum, or a shorter time, or to vary the method in other ways in orderto produce a copper having the desired characteristicsat a lower cost ascompared with completely deoxidized copper.

Itappears that copper oxides present in the copper are decomposed underthe above described conditiqlls causing the oxygen to be eliminated.

The elimination of this oxygen improves the conductivity of the copperand simultaneously improves the workability of the copper. Other gaseswhich are absorbed, adsorbed, or dissolved in the molten copper are alsoremoved from the copper, and their eliminationincreases the density ofthe copper, thereby, further improving its conductivity and workability.By carrying the process to the point where the oxygen content by weightis approximately .0l%, a product is obtained without unduecost having aconductivity approaching the theoretical ideal of pure deoxidized copperconductivity and having high density. The low oxygen content and/orincreased density result in workability equal to or in excess of thebest grades of copper heretofore commercially produced.

In some instances it may be desired to deoxidize native or cathodecopper. In that event a reducin}; gas such as hydrogen or carbonmonoxide may be introduced below the surface of the molten copper, orthe reducing gas may be absorbed through the surface of the moltencopper, the absorption being enhanced by the agitation of the copper inthe induction furnace. Other reducing agents which form gas on combiningwith oxygen such as carbon may also be used. The vacuum then removes theoxygen in the same manner as described in connection with tough pitchcopper.

Although the present invention has been described as relating to aspecific type of furnace, and a specific degree of vacuum applied to thecopper during the melting thereof, it is to be understood that the scopeof the invention is limited only by the scope of the appended claims.

What is claimed is:

1. A method of refining copper which consists of inductively heating andmelting the copper, introducing a reducing agent of hydrogen under thesurface of the molten copper to combine with the oxygen, and applying avacuum of the order of 1 to 4 millimeters to promote reactions betweenthe reducing agent and. the oxygen to remove the oxygen from the copper.

2. A method of refining copper containing oxygen and reducing gasesincluding hydrogen and carbon monoxide which consists of melting thecopper, and applying a vacuum of the order of 1 to 4 millimeters topromote reactions between the oxygen and reducing gases to liberate themfrom the copper.

3. A method of refining copper which consists of heating the copper to atemperature of substantially 1150 C.-to melt the copper, agitating themolten copper, applying a vacuum in the neigh-- borhood of 2 millimetersand introducing a reducing gas of carbon monoxide under the surface ofthe molten copper to remove oxygen.

4. A method of refining copper which comprises melting a partiallydeoxidized copper, introducing a reducing gas of carbon monoxide underthe surface of the molten copper and applying a vacuum in theneighborhood of 1 to 4 millimeters to decompose the copper oxide in thecopper and form a gaseous reaction product, and removing the reactionproduct bysaid vacuum.

5. A method of producing substantially deoxidized copper, whichcomprises poling molten copper whereby hydrogen and carbon monoxidegases, are introduced into the copper, applying a on vacuum of the orderof -1 to 4 millimeters to the molten copper to promote a, reactionbetween said gases and the oxygen of the copper oxide present in themolten copper, and withdrawing the reaction products by the appliedvacuum.

6. A method of refining copper containing oxygen in the form of copperoxide, hydrogen, and carbon monoxide gases, which comprises applying avacuum at a pressure of not more than 4 millimeters to said copper inthe molten state 170 to promote a reaction between the oxygen of thecopper oxide and said gases, and withdrawing the reaction products bythe applied vacuum.

7. A method of refining copper containing oxygen in the form of copperoxide and carbon monoxide, which comprises applying a vacuum at apressure of not more than 4 millimeters to the copper in the moltenstate to promote a reaction between the oxygen in the copper oxide, andthe carbon monoxide, and withdrawing the reaction product by the appliedvacuum.

8. A method of refining copper containing oxygen in the form of copperoxide and hydrogen, which comprises applying a vacuum at a pressure ofnot more than 4 millimeters to the copper in the molten state to promotea reaction between the oxygen of the copper oxide and the hydrogen, andwithdrawing the reaction product by the applied vacuum.

9. A method of producing substantially deoxidized copper, whichcomprises poling molten copper to reduce the oxygen content to .03% to.06% whereby hydrogen and carbon monoxide gases are introduced into thecopper, applying a vacuum at a pressure of not more than 4 millimetersto the molten copper to promote a reaction between said gases and theoxygen of the copper oxide present in the molten copper, and withdrawingthe reaction products by the applied vacuum.

JAMES w. sco'r'r.

